Just how bad are dispersants?

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As we all know, on May 20, the EPA called on BP to use a less harmful dispersant to dissolve the oil gushing into the Gulf of Mexico. According to a notes from a May 27 meeting (PDF) on the long-term impact of dispersants on the Gulf ecosystem, the dispersants are less harmful than simply allowing the oil to wash up on shore, but “much is unknown about the long term environmental impacts of dispersants when used in unprecedented volume and in the subsea.” That means that we don’t know how effective dispersants are when used underwater.

But what do dispersants actually do? And how exactly are they damaging to ecosystems? Popular Science has a great write-up of how oil dispersants work—and what their true impact could be.What are dispersants?According to Popular Science, “Corexit, the dispersant BP is currently using, contains six chemicals. The exact recipe is a secret, according to Corexit’s manufacturer, Nalco, but it contains a surfactant and a solvent. Surfactants are long molecules that are hydrophilic (water-seeking) on one end and oleophilic (oil-seeking) on the other. One end grabs an oil molecule, the other, a water molecule. By reaching across the oil-water boundary, the surfactant lowers the tension that keeps the two substances separate.”

What kind of impact do they have?According to Popular Science, “Dispersants have never been applied on this scale, leaving environmental scientists guessing about the consequences. Corexit may have caused seven cleanup workers to be admitted to the hospital with shortness of breath and nausea.”

Of course there are also concerns regarding the impact of dispersants on wildlife and undersea plants. According to this study, when applied in small amounts to Mallard eggs, Corexit is as fatal as raw crude oil.

James D: "BP should be placed into receivership by the government (quite legal and doable under current law). The government should completely take over the leak stop and clean up operations."

I have never heard anything so stupid! What on earth do governments know about drilling for oil or cleaning up after such tragedies as this? BP are the lease operator of Mississippi Canyon Block 252 (MC252), the oil field where the accident happened. That means they own the right to extract oil but what about Transocean who own and operate the actual drilling rig and Halliburton who were pumping cement slurry into the drill hole prior to the Horizons explosion and are responsible for the pipework. This may yet prove to have been at fault. Should Transocean and Halliburton also be put into receivership? Trying to put the blame on one company in such a complex operation as deep sea drilling for oil even before the problem has been solved, let alone before holding an enquiry into what the causes were, is premature and totally irresponsible.